Natural logs solve ln⁡((x-1)/(x-3))=2

  • MHB
  • Thread starter blackfriars
  • Start date
  • Tags
    Natural
In summary, the conversation discusses a problem involving natural logs and finding the value of x in the equation ln((x-1)/(x-3)) = 2. The solution was provided as x = 2/(e^2-1) ≈ 0.3130352855, but the lecturer gave a different solution of (3e^2-1)/(e^2-1) ≈ 3.313035285. The conversation ends with a request for help in transposing the formula to make x the subject.
  • #1
blackfriars
21
0
hi , hope someone can help as i can't get past a certain step
the natural logs is the problem
ln⁡((x-1)/(x-3))=2
i can get to this point here -1 = e_x^2-x-3
-1+3=x(ⅇ^2-1)
2 = x(ⅇ^2-1)
2/((ⅇ^2-1) )=x((ⅇ^2-1)/(ⅇ^2-1))
X = 2/(ⅇ^2-1)
the solution i got was this x= (2/(ⅇ^2-1)) → 0.3130352855

but the lecturer gave a solution of
(3ⅇ^2-1)/(ⅇ^2-1) = 3.313035285 how do i get to this
 
Mathematics news on Phys.org
  • #2
blackfriars said:
hi , hope someone can help as i can't get past a certain step
the natural logs is the problem
ln⁡((x-1)/(x-3))=2
i can get to this point here -1 = e_x^2-x-3
-1+3=x(ⅇ^2-1)
2 = x(ⅇ^2-1)
2/((ⅇ^2-1) )=x((ⅇ^2-1)/(ⅇ^2-1))
X = 2/(ⅇ^2-1)
the solution i got was this x= (2/(ⅇ^2-1)) → 0.3130352855

but the lecturer gave a solution of
(3ⅇ^2-1)/(ⅇ^2-1) = 3.313035285 how do i get to this
If $\ln\left(\frac{x-1}{x-3}\right) = 2$ then $\frac{x-1}{x-3} = e^2.$ Multiply both sides by $x-3$ to get $x-1 = (x-3)e^2.$ Then rearrange that as $x(e^2 - 1) = 3e^2 - 1$. That gives $x = \dfrac{3e^2-1}{e^2-1} \approx 3.313035...$.
 
  • #3
hi sorry for the questions but i cannot transpose the formula to make x the subject could you show the workings for making x the subject
thanks
 
  • #4
Same topic and a working found http://mathhelpboards.com/pre-algebra-algebra-2/logs-22167-new.html. Thread closed - please continue discussion in linked thread.

blackfriars, please do not post duplicate topics; thanks. :D
 

FAQ: Natural logs solve ln⁡((x-1)/(x-3))=2

What is a natural log?

A natural log (ln) is a mathematical function that is the inverse of the exponential function. It is written as ln(x) and represents the power to which the mathematical constant e (approximately 2.71828) must be raised to equal x.

How do I solve for x in ln⁡((x-1)/(x-3))=2?

To solve for x in this equation, you can use the properties of logarithms and algebraic manipulation. First, you can use the property ln(a/b) = ln(a) - ln(b) to rewrite the equation as ln(x-1) - ln(x-3) = 2. Then, you can use the property ln(a^b) = b*ln(a) to rewrite the equation as ln((x-1)/(x-3)) = ln(e^2). Finally, you can take the inverse of the natural log function to get (x-1)/(x-3) = e^2. You can then solve for x using algebraic methods.

Can I use a calculator to solve this equation?

Yes, you can use a calculator to solve this equation. Most scientific calculators have a natural log function (ln) and can perform the necessary calculations to find the solution for x.

What if I get a negative number as the solution for x?

If you get a negative number as the solution for x, it is important to double check your calculations and make sure you didn't make any mistakes. If you are confident in your calculations and still get a negative number, it may be a valid solution depending on the context of the problem. For example, if the equation represents a decay process, a negative solution for x could make sense.

How can I check my answer?

You can check your answer by plugging your solution for x back into the original equation and seeing if it satisfies the equation. You can also use a graphing calculator or graphing software to graph both sides of the equation and see if they intersect at your solution for x.

Similar threads

Replies
6
Views
2K
Replies
44
Views
4K
Replies
2
Views
1K
Replies
1
Views
904
Replies
3
Views
858
Replies
4
Views
1K
Replies
1
Views
1K
Replies
1
Views
931
Replies
1
Views
837
Back
Top